Description

• Common benign tumor of the epidermis formed from proliferation of keratinocytes
• Frequently appears in multiples on the head, neck, and trunk (sparing the palms and soles) of older individuals but may occur on any hair-bearing area of the body
• Typically presents as multiple, well-circumscribed, yellow to brown raised lesions that feel greasy, velvety, or warty; usually described as having a “stuck-on” appearance
• Clinical variants include the following:
  • Common seborrheic keratosis
  • Dermatosis papulosa nigra
  • Stucco keratosis
  • Flat seborrheic keratosis
  • Pedunculated seborrheic keratosis
• Synonym(s): SK, verruca seborrhoica; seborrheic wart; senile wart; basal cell papilloma; verruca senilis; benign acanthokeratoma; barnacles of aging

Epidemiology

Incidence

• Predominant age: appear most commonly in those aged 31 to 50 years, and incidence increases with age, peaking at age 60 years
• Predominant sex: slightly more common and more extensive involvement in males
• Most common among Caucasians, except for the dermatosis papulosa nigra variant, which usually presents in darker skinned individuals

Prevalence

• 69–100% in patients >50 years of age
• The prevalence rate increases with advancing age.

Etiology and Pathophysiology

• Etiology remains largely unclear with ultraviolet (UV) light and genetics thought to be involved.
• The role of human papillomavirus is uncertain.

Genetics
An autosomal dominant inheritance pattern is suggested.

Risk Factors

• Advanced age
• Exposure to UV light and genetic predisposition are the possible factors.

General Prevention

Sun protection methods may help prevent seborrheic keratoses from developing.

Commonly Associated Conditions

• Sign of Leser-Trélat: a paraneoplastic syndrome characterized by a rapid outbreak of multiple seborrheic keratoses often associated with an internal malignancy, most commonly adenocarcinoma; seborrheic keratosis may resolve with treatment of the malignancy and reappear with neoplasm recurrence.
• Documentation of other cutaneous lesions, such as basal cell carcinoma, malignant melanoma, or squamous cell carcinoma, growing adjacent to or within a seborrheic keratosis, has been reported. The exact relationship between lesions is unclear.